Stable-hydrogen isotope measures of natal dispersal reflect observed population declines in a threatened migratory songbird

Studds, Colin E., McFarland, Kent P., Aubry, Yves, Rimmer, Christopher C., Hobson, Keith A., Marra, Peter P. and Wassenaar, Leonard I. (2012) Stable-hydrogen isotope measures of natal dispersal reflect observed population declines in a threatened migratory songbird. Diversity and Distributions, 18 9: 919-930. doi:10.1111/j.1472-4642.2012.00931.x


Author Studds, Colin E.
McFarland, Kent P.
Aubry, Yves
Rimmer, Christopher C.
Hobson, Keith A.
Marra, Peter P.
Wassenaar, Leonard I.
Title Stable-hydrogen isotope measures of natal dispersal reflect observed population declines in a threatened migratory songbird
Journal name Diversity and Distributions   Check publisher's open access policy
ISSN 1366-9516
1472-4642
Publication date 2012-09
Sub-type Article (original research)
DOI 10.1111/j.1472-4642.2012.00931.x
Volume 18
Issue 9
Start page 919
End page 930
Total pages 12
Place of publication Oxford, United Kingdom
Publisher Wiley-Blackwell Publishing
Collection year 2013
Language eng
Formatted abstract
Aim
Measuring dispersal is crucial for estimating demographic rates that inform conservation plans for rare and threatened species. We evaluated natal dispersal patterns in Bicknell's thrush (Catharus bicknelli) across most of the breeding range using a 10-year data set of stable-hydrogen isotope ratios in feathers (δ2HF) grown on the natal area and sampled 1 year later at the first breeding site.

Location

North-eastern United States and south-eastern Canada.

Methods
We used δ2HF values of adult thrushes sampled at 25 breeding sites as prior information for assigning first-time breeders to their natal site. We calculated the minimum distance birds moved from their natal to first breeding site and fit these data to three statistical distributions for characterizing the importance of long-distance dispersal: the exponential, Weibull and half-Cauchy. Finally, we assessed differences in the probability of dispersal across the breeding range and through time to understand spatio-temporal variation in demographic connectivity.

Results

The δ2HF values of first-time breeders were lower compared with those of adults, a difference that was greater at the southern compared with northern breeding range extreme. Assignment tests accounting for age differences in δ2HF suggested that most birds dispersed < 200 km from their natal area and within the centre of the breeding range, whereas comparatively few individuals dispersed up to 700 km. A Weibull distribution provided the best fit to these data. Two of three corrections for age differences in δ2HF indicated that natal dispersal probability declined by 30–38% from 1996 to 2005.

Main conclusions

Our findings suggest that estimating natal dispersal with δ2HF measurements may contribute to understanding the resilience of geographically isolated Bicknell's thrush populations. Declining natal dispersal may be symptomatic of observed population declines and could compound this trend by limiting demographic exchange between habitat patches predicted to be increasingly isolated by natural and anthropogenic habitat changes.
Keyword Bicknell's thrush
Conservation biogeography
Dispersal
Movement ecology
Neotropical-Nearctic migratory bird
Population declines
Stable isotopes
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Official 2013 Collection
School of Biological Sciences Publications
 
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Created: Sat, 15 Sep 2012, 15:54:12 EST by Gail Walter on behalf of School of Biological Sciences